The input unit of modern radio devices typically provides a very high input dynamic in order to receive radio signals over the widest possible radio range. This input dynamic of an input unit generally exceeds the dynamic range of signal processing units in radio devices, such as, filters or analog/digital converters. However, to achieve a high dynamic, automatic gain control circuits (automatic gain control, AGC) are used.
A signal-processing path with several cascaded amplifiers adjustable with regard to their gain factor, the gain factor being adjusted in each case by a control circuit based on a feedback structure (feed-back-structure), is known from JP 2004-080455 A.
An automatic gain control of this kind is only conditionally suitable for amplifiers arranged in the signal path of a radio device, because a feedback control structure is generally associated with poor settling behaviour and therefore provides a poorer time dynamic, and because modern radio devices are operated in a frequency-hop method with comparatively short time slots for message transmission. Moreover, the control structure can tend, dependent upon its structure, towards unstable behaviour, which is not acceptable for secure message transmission, for example, in aeronautical radio technology.
Accordingly, there is a need for a device with automatic gain and/or attenuation control for amplification and/or attenuation elements disposed in the signal path of a radio device, which provides optimal time behaviour.